During most surgical procedures the patient is paralyzed and must depend completely on the anesthesiologist to maintain such vital physiologic functions as breathing and heart rate. It is therefore not surprising that with relatively few effective physiological monitors available to the anesthesiologist, the frequency of mishaps is high. Of the approximately 20 million surgical procedures preformed annually in this country, it is estimated that about 6,000 people die or become seriously disabled as a result of the anesthetic procedure. Anesthesia monitoring can be divided into 1) monitors which primarily check the performance of the anesthesia delivery system and 2) monitors which are aimed at measuring the physiological effects of anesthetics the cardiopulmonary status of the patient. The goal of this proposed work is to extend the capabilities of monitoring systems (presently designed for performance checking) for monitoring of cardiopulmonary variables. The proposed system will be capable of continuously monitoring of cardiopulmonary variables. The proposed system will be capable of continuously monitoring cardiac output, alveolar ventilation, and blood gases. A key to economical and high quality measurements of these cardiopulmonary parameters is the ulitization of a quality analyzer already competitively priced for service as an anesthetic gas monitor. Since the analyzer represents the major cost of a total anesthesia/physiologic monitoring system, the physiological monitoring addition represents a very substantial monitoring benefit at a disproportionately modest cost.